A month after losing his powerful spot atop the state legislature amid an ongoing federal corruption probe, former Illinois House Speaker Michael Madigan announced Thursday he will resign from the Illinois House.

His resignation as a representative of his Southwest Side district comes more than 50 years after his unprecedented career in American politics began.

In his announcement Thursday, Madigan made no mention of the corruption probe circling him but defended his career in public office and offered a blistering attack at critics who blame him for many of the ills plaguing Illinois government.

“It’s no secret that I have been the target of vicious attacks by people who sought to diminish my many achievements lifting up the working people of Illinois. The fact is, my motivation for holding elected office has never wavered,” Madigan said in a prepared statement. “I leave office at peace with my decision and proud of the many contributions I’ve made to the state of Illinois, and I do so knowing I’ve made a difference.”

Madigan’s move was not a total shock after he lost the speakership in January following an uprising by several House Democrats who challenged his historic tenure. Madigan was first elected first state representative in 1970 and became the longest-serving state speaker in U.S. history, having headed the House for all but two years since 1983.

Last month, House members selected state Rep. Emanuel “Chris” Welch, a Madigan ally, to replace him, a move that also made Welch the first Black speaker in state history. Madigan remains head of the Illinois Democratic Party and continues to be the Democratic committeeman for the 13th Ward.

Long considered one of the most powerful politicians in the state, Madigan’s grip began to weaken amid an ongoing federal investigation, as well as persistent claims of sexual harassment by some members of his vast political army.

Madigan made no mention of either issue in his statement Thursday. Instead, he touted his work diversifying the House Democratic caucus, his stance on issues that affect middle-class families, his work on school funding, his positions on worker rights and his support for marriage equality.

He also noted his role overseeing the impeachment of former Gov. Rod Blagojevich, a fellow Democrat, and portrayed himself as a firewall against efforts by former Republican Gov. Bruce Rauner’s administration to weaken unions and create economic havoc across the state.

“We stood up for working people,” Madigan said. “Rauner went on to plunge our state into a budget crisis, nearly bankrupting social service agencies, eliminating funding for higher education, and racking up billions of dollars in state debt in the process. House Democrats stood as the last line of defense to protect our state from collapse.”

But any successes Madigan achieved during the Rauner years faded in recent years.

In July, federal charges against utility giant Commonwealth Edison singled Madigan out as “Public Official A” in an alleged corruption scheme. Madigan, 78, has not been charged and he has said he has done nothing wrong.

The filing, in which ComEd agreed to pay a $200 million fine and cooperate in the federal corruption probe, alleged a “years-long bribery scheme” in which ComEd steered contracts, jobs and payments to Madigan allies.

Madigan’s vast influence in state and city government is well documented, including his practice of securing private and public jobs for members of his political army and other loyalists.

The court filings last July said ComEd and others close to Madigan worked to influence the longtime speaker as part of a corrupt scheme for favorable legislation.

Federal authorities charged longtime Madigan political ally and lobbyist Michael McClain, former Exelon chief executive Anne Pramaggiore, the utility’s lobbyist John Hooker, and Jay Doherty, a lobbyist and the former head of the City Club of Chicago, an influential civic group.

In November, Pramaggiore, Hooker, Doherty and McClain were all charged with bribery conspiracy, bribery and willfully falsifying ComEd books in connection with the scheme. They have denied the charges.

The charges came more than a year after the Better Government Association and WBEZ first reported ComEd’s involvement in the sweeping corruption probe after federal agents in May of 2019 raided the homes and businesses of ComEd lobbyists as well as politicians with ties to Madigan, seeking records tied to the speaker.

Democratic Gov. J.B. Pritzker in November, as well as U.S. Sen. Dick Durbin, said Madigan’s damaged public persona led to the defeat of some Democratic candidates and the governor’s top initiative to change the state’s income tax system.

“The people of Illinois have much to be grateful for thanks to his dedicated public service, and the many sacrifices he and his family made to make a difference in our lives,” Pritzker said in a statement Thursday.” I know how dearly he loves his wife Shirley, their children and grandchildren, and I hope that in this next chapter, his family can begin to make up for lost time.”